to get and set request parameters. I couldn't seem to find an equivalent in mod_perl 2, Apache2::Request allows retrieving parameters by its param() method, but no way to set the parameters to be processed further down the chain, thanks.

What you're doing here (changing the actual input) is kind of a bad idea. It would be better to use some kind of internal data structure for passing around your processed parameters, maybe storing them in a hash in $r->pnotes().

Well, you have to change code that uses $r->args to parse the query string because that doesn't work anymore. See the porting doc for more info. You can set the complete query string with $r->args(), which might allow later code to see your parameter changes, or you might be able to use Apache2::Request and modify the params using the APR::Table API on the object it returns when you call it like this: